Reviews are systematic reviews and/or meta-analyses of the primary literature. We will perform a review only if valid and timely guidelines, systematic review or meta-analyses are NOT available in the literature. Examples of the types of decisions our reviews inform include those that a task force make during the development of an evidence-based clinical practice guideline, or those that our technology committees make when considering the purchase of a product. Every guideline that we develop is informed by a review, but not every review results in a clinical practice guideline.